diff --git a/lib/progress_bar/with_progress.rb b/lib/progress_bar/with_progress.rb
index a0a8ab8..10fe54c 100644
--- a/lib/progress_bar/with_progress.rb
+++ b/lib/progress_bar/with_progress.rb
@@ -3,7 +3,7 @@
 class ProgressBar
   module WithProgress
     def each_with_progress(*args, &block)
-      bar = ProgressBar.new(count, *args)
+      bar = ProgressBar.new(respond_to?(:size) && size || count, *args)
       if block
         each{ |obj| yield(obj).tap{ bar.increment! } }
       else